Press Releases

Findings support SER-109 Phase 3 program as a potential new treatment
option for C. difficile infection

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Oct. 3, 2018--
Seres
Therapeutics, Inc. (Nasdaq:MCRB) today announced it will present new
data for SER-109, a microbiome candidate in Phase 3 development, at the
IDWeek 2018 conference being held from October 3-7 in San Francisco, CA.
The findings, highlighted in two presentations, provide support for
SER-109 as a potential new treatment option for individuals suffering
from recurrent C. difficile infection. The company will also host
a symposium on the development on novel microbiome therapeutics for C.
difficile infection.

“These additional SER-109 data provide valuable information about the
potential mechanism of action of microbiome therapeutics, an emerging
new field of medicine. Our results provide additional evidence
supporting the continued development of SER-109 in patients with
recurrent C. difficile infection. In addition, these new data
suggest that SER-109 may have important broader public health benefits
by reducing the spread of antibiotic resistance,” said Matthew
Henn, Ph.D., Executive Vice President, Microbiome Research and
Development at Seres Therapeutics.

C. difficile infection is often treated with extended antibiotic
regimens, resulting in damage to the natural gastrointestinal microbiome
and proliferation of antibiotic resistant bacteria1. Data
from Ford et al., based on analysis of SER-109 Phase 2 study
samples, demonstrate that SER-109 administration increases microbiome
diversity and that outgrowth of SER-109 bacteria is associated with a
reduction in the abundance of antibiotic resistance genes in subjects’
gastrointestinal tract. These new results suggest that microbiome
therapeutics have the potential to address the spread of antibiotic
resistance, a major public health concern.

In a separate presentation, Henn et al. show that SER-109 administration
and subsequent bacterial outgrowth leads to changes in the metabolic
products created by the gastrointestinal microbiota, including higher
concentrations of secondary bile acids. Secondary bile acids are
generated by bacteria residing in the gut, and published studies suggest
that these molecules inhibit the growth of C. difficile2.
The findings provide important insights into the potential mechanism of
action of SER-109 for C. difficile infection.

Seres Therapeutics, Inc. (Nasdaq:MCRB) is a leading microbiome
therapeutics platform company developing a novel class of biological
drugs that are designed to treat disease by restoring the function of a
dysbiotic microbiome, where the state of bacterial diversity and
function is imbalanced. Seres’ lead program, SER-109, has obtained
Breakthrough Therapy and Orphan Drug designations from the U.S. Food and
Drug Administration and is in Phase 3 development for multiply recurrent C.
difficile infection. SER-287 has successfully completed a Phase 1b
study in patients with mild-to-moderate ulcerative colitis. Seres is
developing SER-262, the first ever synthetic microbiome therapeutic
candidate, in a Phase 1b study in patients with primary C. difficile
infection. Seres is also developing SER-401 to augment the efficacy of
immuno-oncology treatment. For more information, please visit www.serestherapeutics.com.
Follow us on Twitter @SeresTx.

This press release contains forward-looking statements within the
meaning of the Private Securities Litigation Reform Act of 1995. All
statements contained in this press release that do not relate to matters
of historical fact should be considered forward-looking statements,
including the ability of SER-109 to prevent the spread of antibiotic
resistance, the ability of ECOSPOR III to support SER-109 approval, and
the promise and potential impact of any of our microbiome therapeutics.

These forward-looking statements are based on management’s current
expectations. These statements are neither promises nor guarantees, but
involve known and unknown risks, uncertainties and other important
factors that may cause our actual results, performance or achievements
to be materially different from any future results, performance or
achievements expressed or implied by the forward-looking statements,
including, but not limited to, the following: we are not currently
profitable and may never become profitable; our need for additional
funding; our limited operating history; our unproven approach to
therapeutic intervention; the lengthy, expensive, and uncertain process
of clinical drug development; protection of our proprietary technology
and the confidentiality of our trade secrets; potential lawsuits for, or
claims of, infringement of third-party intellectual property or
challenges to the ownership of our intellectual property; our patents
being found invalid or unenforceable; and our ability to retain key
personnel and to manage our growth. These and other important factors
discussed under the caption “Risk Factors” in our Quarterly Report on
Form 10-Q filed with the Securities and Exchange Commission, or SEC, on
August 2, 2018 and our other reports filed with the SEC could cause
actual results to differ materially from those indicated by the
forward-looking statements made in this press release. Any such
forward-looking statements represent management’s estimates as of the
date of this press release. While we may elect to update such
forward-looking statements at some point in the future, we disclaim any
obligation to do so, even if subsequent events cause our views to
change. These forward-looking statements should not be relied upon as
representing our views as of any date subsequent to the date of this
press release.